1. FIELD OF THE INVENTION
Wheels for many types of devices including wheels for roller skates, and particularly for skateboards, must be not only functional, durable and reliable, but, at least in part because of the nature of the purchasers and users of the skateboard, the wheels must be esthetically pleasing. The skateboard wheel, just as any other wheel, must have precision dimensional characteristics for good rolling motion. It must be durable, skid resistent, quiet, reliable and, preferably, inexpensive to manufacture. It is found, moreover, that the appearance of the wheel will significantly affect its marketability. Colored transparent wheels are highly desirable for certain uses. Nevertheless, it has not been possible heretofore to provide a transparent wheel with all of these desired characteristics.
2. Description of Prior Art
Good wear resistance and anti-skid characteristics are available from molded polyurethane wheels partly because of the resilient characteristics of this material. However, this very characteristic, the resilience, makes it difficult to provide an accurate wheel, one in which the wheel bearing and thus, the wheel axle, is firmly positioned and securely locked in place. Thus, it has been necessary in the past to provide a rigid washer between a pair of inner bearing races when molding an integral wheel of a material such as polyurethane. The use of the race retaining nylon washer in a cast wheel significantly adds to the time and expense of the manufacturing process. In some instances, such as described in U.S. Pat. No. 3,592,510 to Heitfield, it is attempted to hold the back-to-back bearing races in place by use of a casting material which shrinks upon curing. Such an arrangement is still dependent upon rigidity of the cast material for proper positioning of the wheel body with respect to the bearing races.
It has not been possible heretofore to achieve adequate dimensional precision in cast wheels, at least in part due to the very characteristic, the shrinkage of cured material, which the patentee Heitfield seeks to exploit. As the body of cast plastic cures, its originally cast surface configuration changes and outer surfaces, such as circumferential tread, for example, will tend to become concave, a configuration that is undesirable.
Another esthetic consideration of the skateboard wheel is the positioning of displays, printing, names, insignia or the like, upon the side of the wheel in bold, outstanding and easily visible patterns. In conventional wheel construction, such display patterns on the outside of the wheel are rapidly abraded and worn away and, moreover, are often difficult to see because of flat, angulated side surfaces.
The commonly used and desirable urethane plastic wheel is not transparent since this material in thicknesses required of a full wheel has relatively poor transparency. Further, it is relatively expensive and not readily adapted to provide different colors.
Accordingly, it is an object of the present invention to provide a molded wheel that eliminates or minimizes the above mentioned problems of prior wheels and provides a wheel that maximizes many desirable characteristics.